Acid dyes and cationic dyes have been utilized for many years by carpet manufacturers. Acid dyes are normally referred to as water soluble cationic dyes that are applied to fibers normally using neutral dye acid dye baths. Attachment to the fiber is believed to be attributed at least partly to salt formation between anionic groups and the dyes and cationic groups in the fibers.
Cationic dyes are normally water soluble and may be applied to oppositely charged groups in the fiber to provide salts as well. When utilizing both dye type together in solution with a carpet tufted with both acid and cationic fibers, anti-precipitants are often utilized in the mixture. This technology has been utilized for many years in the carpet industry principally in the form of a solution containing both acid and cationic dyes which are applied in a beck (something akin to a vat) with carpet run therethrough over a period of time. This normally results in two color colorations (from the two dyes) as is known in the art. Since the dyes are normally in a beck, they are free to flow back and forth and normally provide precise attachment to specific fibers in a desired manner. Carpet manufacturers have been doing this for years.
In an effort to reduce energy expenditures, the applicant has been utilizing a continuous dyeing process for a number of years in which carpet is fed through a single application of dye normally proceeding then through at least one steamer. Location of cationic and acid fibers have been precisely provided so that dyes would not bleed over into locations. Providing first run carpet is a principal object of dyeing operations.
To the applicant's knowledge, no company has intentionally created a carpet providing a fade over at least a few tuft stitches if not over a few inches somewhat akin to an old art dying look. In modern carpet manufacturing techniques such as construction would not be believed to be obvious from current construction methods as it would have appeared as a “second” quality good and discarded for not complying with an intended sample pattern.